1. Field of the Invention
The present invention relates to an apparatus which will be capable of performing the arithmetic functions of addition, subtraction, multiplication and division and the functions of conversion where the data entered into the apparatus is in measurement of feet, inches and fractions of an inch and also in decimal and metric measurement equivalents of feet, inches and fractions of an inch.
2. Technical Considerations and Prior Art
Currently available electronic calculators basically utilize a keyboard with ten character keys identified by and idenntifying the digits zero to nine, and the four function keys identified by signs representing the arithmetic functions of addition (+), subtraction (-), multiplication (.times.) and division (.div.), plus a key identified as an equal (=) key for finalizing the arithmetic functions of multiplication and division and, in some models, for addition and subtraction. There are generally other auxiliary keys or switches such as the "clear" key, "clear entry" key, and "decimal selector" switch, to set the decimal at a predetermined place (2 places, 3 places, etc.), or to permit the decimal to "float." Some calculators have "percent" keys, "square" keys, "square root" keys, "reciprocal" keys, "memory" keys, trigonometric conversion keys, metric mesurement conversion keys, and other auxiliary keys.
The construction and operation of currently available electronic calculators is well known to those familiar with and skilled in the art of electronic calculators.
However, with currently available electronic calculators, calculations in feet, inches and fractions of an inch (hereinafter referred to as "fractions") cannot be directly performed except where "feet" is exact, or in metric equivalent obtained from printed conversion tables, and except where the feet-inch-fraction numeric is converted into decimal equivalent or metric equivalent, also by the use of equivalency tables. For example, two measurements of 2 feet 6 inches and 6 feet 3 inches cannot be directly added together, but must first be converted into decimal equivalents of 2.5 feed and 6.25 feet, respectively, and then entered into the calculator and added, thus: 2.5 plus (+) 6.25 equals (=) 8.75. The user would then have to mentally convert 8.75 feet to 8 feet 9 inches.